1. Field of the Invention
This invention relates to a two-dimensional scanning apparatus and a scanning type image displaying apparatus using the same, and particularly is adapted to two-dimensionally scan a beam (deflected beam) deflected by deflecting means to thereby project and display a two-dimensional image on a surface to be scanned (a screen surface).
2. Related Background Art
There have been proposed various two-dimensional scanning apparatuses which two-dimensionally deflect a beam emitted from light source means by deflecting means, two-dimensionally optically scan on a surface to be scanned by a spot, and form a two-dimensional image by the afterimage effect thereof (see, for example, Japanese Patent Application Laid-open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583).
Now, it is known that by a beam being two-dimensionally deflected and scanned, so-called distortion occurs to a two-dimensional image on a surface to be scanned. The distortion includes trapezoid distortion, distortion of a uniform speed scanning property, distortion of a rectilinear scanning property and further, TV distortion which refers to the curving of the frame of an image depicted on the surface to be scanned.
In Japanese Patent Application Laid-open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583, there is disclosed a two-dimensional scanning apparatus using an optical element including a refracting surface and a reflecting surface, and adapted to turn back an optical path in the interior of the optical element (prism member), and in which in order to correct eccentric aberration, the refracting surface or the reflecting surface is constituted by a non-rotation symmetric surface having no rotation symmetry axis either inside or outside the surface.
This is a two-dimensional scanning apparatus constituted by the use of an optical element, and yet well corrects uniform velocity property of scanning light on the surface to be scanned over a wide scanning angle. It can also achieve telecentricity necessary for highly accurate image depiction.
However, the two-dimensional scanning apparatus disclosed in Japanese Patent Application Laid-open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583 does not at all correct TV distortion. Further, when an image has been obliquely projected onto a surface to be scanned such as a screen, trapezoid distortion has occurred to thereby deteriorate the dignity of the image, the two-dimensional scanning apparatus disclosed in Japanese Patent Application Laid-Open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583 neither correct trapezoid distortion.